Engine ignition system

ABSTRACT

An engine ignition system connected between an engine crank and ignition coils includes a reference position signal generating device having reference position sensors, and a crank angle sensing device. The ignition system also includes a signal processing device which receives both the reference position signals and crank angle signals, and when one of the reference position signals is absent continues to generate ignition control signals which activate the ignition coils. The signal processing device includes a counter which counts the crank angle signals and which is reset by the reference position signals, and a decoder which produces a signal when a count value reaches a predetermined count. The signal processing device also includes a logic circuit and a flip-flop for producing either primary ignition control signals or replacement ignition control signals. The replacement ignition control signals are generated when one of the reference position signals is absent.

BACKGROUND OF THE INVENTION

The present invention relates to an engine ignition system for maintaining the generation of ignition control signals even when part of an ignition timing control system is malfunctioning.

The ignition timing of the engine is controlled using a reference position detecting sensor for detecting the position of the engine pistons. In the prior art pulses are generated to control the ignition timing by arithmetically processing both a signal from a reference position detecting sensor and a signal from a crank angle detecting sensor which detects the rotational angle of the engine. Within the reference position detecting sensor is a magnetic sensor containing a fine wire coil which can be broken. If the coil breaks, the reference position detecting signal is not generated and the engine will not run.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ignition system for generating ignition pulses at a proper timing even when a reference position detecting sensor is malfunctioning and a reference position detecting signal is blocked.

The present invention includes an engine crank angle sensing device which generates crank angle signals, and a reference position signal which generates device generating reference position signals. The invention also includes a signal processing device connected to a switching circuit for the engine ignition coils. The signal processing device detects the loss of one of the reference position signals and generates a replacement signal. The signal processing device includes a counter which counts the crank angle signals, and a decoder which outputs a signal when the count reaches a predetermined value. The signal processing device also includes a logic circuit connected to the decoder, a flip-flop, the switching circuit and the reference position signal generating device. The logic circuit generates the replacement signals when one of the reference position signals is absent and the decoder outputs a signal.

These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a first embodiment of an engine ignition system according to the present invention;

FIG. 2 is a time chart illustrating signals in the circuit of FIG. 1 in its normal state;

FIG. 3 is a time chart illustrating signals in the circuit of FIG. 1 in an abnormal state;

FIG. 4(a) is a table tabulating crankstrokes of a series four-cylinder engine;

FIG. 4(b) is a table tabulating crankstrokes of a series two-cylinder engine;

FIG. 5 is a circuit diagram illustrating a second embodiment of the present invention;

FIG. 6 is a time chart illustrating signals in the circuit of FIG. 5 in a normal state; and

FIG. 7 is a time chart illustrating signals in the circuit of FIG. 5 in an abnormal state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Engines of existing vehicles are classified into the following categories: series two-cylinder, series four-cylinder, series six-cylinder, V-type two-cylinder having a 360 degree crank, and a series two-cylinder having a 180 degree crank. Each of these types of engines have different positions for mounting reference position detecting sensors because of their different cylinder arrangements.

A block diagram of a first embodiment of the present invention is illustrated in FIG. 1 and is applied to the series four-cylinder engine having a 360 degree crank and a series two-cylinder engine having a 180 degree crank.

Reference magnetic disc P₁ is secured to a crankshaft J₁ of the engine by a second shaft or other device for rotating the disc P₁ and has formed on the outer circumference of the disc P₁ a tooth a. Reference magnetic sensors SN₁ and SN₂ are positioned about the periphery of the magnetic disc P₁ at diametrically opposite positions so that they act as reference position detecting magnetic sensors. Each time tooth a of the magnetic disc P₁ passes either of the magnetic sensors SN₁ or SN₂ because of the rotation of the crankshaft J₁, the corresponding magnetic sensor SN₁ or SN₂ generates a pulse signal S₁ or S₂. Crank angle magnetic disc P₂ is also secured to crankshaft J₁ by a shaft or other device for rotating the disc P₂ and has formed on its outer circumference 180 teeth b spaced 2 degrees apart. A crank angle magnetic sensor SN₃ generates a pulse signal each time one of the teeth b of the magnetic disc P₂ rotates past the magnetic sensor SN₃ due to the rotation of the crankshaft J₁. In other words, when the crankshaft J₁ rotates 2 degrees a pulse signal S₃ is generated.

Waveform shaping circuits 1, 2 and 3 receive the pulse signals S₁, S₂ and S₃, respectively. The pulse signals S₁ and S₂ have their waveforms shaped so that square wave signals S₄ and S₅ having identical pulse widths are produced by the waveform shaping circuits 1 and 2. The waveform shaping circuit 3 produces a square wave signal S₆ which has a smaller width than signals S₄ and S₅. Signal S₆ is used as a crank angle pulse signal for indicating the unit angle rotation of the crankshaft J₁. A trailing edge differential circuit 4 receives the square wave signal S₄ and generates differential pulses by differentiating the trailing edge of the square wave signal S₄. The differential pulses are used as first reference position pulses S₇. A trailing edge differential circuit 5 also generates differential pulses, by differentiating the trailing edge of the square wave signal S₅, and these differential pulses are used as second reference position pulses S₈. An OR circuit 6 receives the first and second reference position pulses S₇ and S₈ and generates a pulse signal S₉ which is the logical sum of the pulses S₇ and S₈. A counter 7 receives the crank angle pulses S₆ at its clock pulse input terminal CP and receives the signal S₉ at its reset terminal R. Counter 7 counts 90 pulses within the signal S₆ and outputs the counted value in a binary code. The counter 7 is normally cleared by the signal S₉ which is produced before the counted value reaches 90, so that all the counted value outputs are held at a low level. A decoder 8 receives the counted value binary code generated by the counter 7 and determines whether the signal S₉ is received by the counter before a predetermined timing. When the counted value is greater than or equal to 90 a pulse signal S₁₀, having a predetermined pulse width, is generated. A leading edge differential circuit 9 receives the signal S₁₀ and generates differential pulses S₁₁ by differentiating the leading edge of the signal S₁₀. An AND circuit 10 receives both the pulse signal S₁₁ and a later-described pulse signal S₁₈ and generates a signal S₁₂. An AND circuit 11 receives both the pulse signal S₁₁ and a later-described signal S₁₉ and generates signal S₁₃. An OR circuit 12 receives the signal S₇ from the trailing edge differential circuit 4 and the signal S₁₂ from AND gate 10, and generates a signal S₁₄ which is the logical sum of the input signals. An or gate 13 receives the signal S₈ from the trailing edge differential circuit 5 and the signal S₁₃ from the AND gate 11, and generates a signal S₁₅ which is the logical sum of the input signals. A trailing edge differential circuit 14 generates differential pulses by differentiating the trailing edge of the signal S₁₅ and a trailing edge differential circuit 15 generates differential pulses S₁₇ by differentiating the trailing edge of the signal S₁₄. A flip-flop circuit 16 receives at its set terminal S the differential pulses S₁₆ and at its reset terminal R the differential pulses S₁₇, and outputs from its output terminals Q and Q, the pulse signals S₁₈ and S₁₉, respectively, which are inverted with respect to each other.

The signal S₁₄ is received by the base of a transistor TR₁ which comprises a switching circuit for an igniter and which has its emitter grounded. The collector of transistor of TR₁ is connected to a primasry winding terminal of an ignition coil T1. The other terminal of the primary winding coil T1 has a voltage +B applied thereto. The secondary winding of the ignition coil T1 has one terminal grounded through an ignition plug #1 nad its other terminal grounded through an ignition plug #4. Similarly, the signal S₁₅ is received by the base of transistor TR₂ which comprises a switching circuit for an igniter and which has its emitter grounded. The collector of transistor TR₂ is connected to a primary winding terminal of ignition coil T₂. The other terminal of the primary winding has applied thereto the voltage +B. The secondary winding of ignition coil T₂ has one terminal grounded through an ignition plug #3 and has its other terminal grounded through an ignition plug #2.

The operation of the circuit illustrated in FIG. 1 will be described with reference to FIG. 2 which illustrates a time chart for the signals in the circuit during normal operation.

At a time between t₁ and t₂ when the tooth a of magnetic disc P₁ passes the magnetic sensor SN₁, the pulse signal S₁ is generated and output as the square wave signal S₄. At a time between t₃ and t₄ when the engine has rotated 180 degrees, the pulse signal S₂ is generated when tooth a passes magnetic sensor SN₂ and is output as square wave signal S₅. When the trailing edge differential circuit 4 detects the trailing edge of the signal S₄, the position detection pulse S₇ is generated at the time t₂. When the trailing edge differential circuit 4 detects the trailing edge of the signal S₅ another position detection pulse S₈ is generated at the time t₄. As a result, the signal S₉ which is composed of both the position detection pulses S₇ and S₈, becomes high, and the counter 7 is reset by signal S₉ each time the engine makes one half of a rotation. During this time the clock pulse terminal CP of the counter 7 receives the square wave signal S₆ which is obtained from the waveshapping circuit 3 which shapes the crank angle pulses S₃ generated each time the engine rotates 2 degrees. If the counter 7 counts 90 square waves the decoder 8 outputs the signal S₁₀. However, in a normal operating state, the counter 7 is reset by the signal S₉ before the count reaches 90 and the signal S₁₀ is held unchanged at a low level. As a result, the output signal S₁₁ generated by the leading edge differential circuit 9 is held at the low level, and the signals S₁₂ and S₁₃ output by the AND circuits 10 and 11, respectively, are also held at the low level. Consequently, signal S₁₄ output by the OR circuit 12 is coincident with the position detection pulses S₇, and the signal S₁₅ output by the OR circuit 13 is coincident with the position detection pulses S₈. Thus, each time the crankshaft J₁ makes a half rotation, the signals S₁₄ and S₁₅ are generated, and act as ignition control signals to alternately activate the transistors TR₁ and TR₂ of the igniters. The signals activating the transistors TR₁ and TR₂ are output as voltage-boosted pulses to the secondary terminals of the ignition coils T₁ and T₂ thereby consecutively sparking the ignition plugs #1 to #4.

The operation of the circuit illustrated in FIG. 1 in an abnormal state when the magnetic sensors SN₁ or SN₂ have their coils broken will be described with reference to FIG. 3. For this example it is assumed that the magnetic sensor SN₁ is broken during the period between time t₄ and time t₅.

Since the position detection pulse S₇ is generated at time t₂, the ignition control signal S₁₄ dependent thereon turns the transistor TR₁ on and off, so that the ignition plugs #1 and #4 are alternately sparked. At the time t₄, since the ignition detection pulse S₈ is generated, the ignition control signal S₁₅ is generated turning the transistor TR₂ on and off, so that the ignition plugs #2 and #3 are alternately sparked. If it is assumed that the magnetic sensor SN₁ has its coil broken after the time t₄ the square wave signal S₄ is not generated at time t₅, so that the position detection pulse S₇ is not generated. Since the flip-flop circuit 16 is held in its set state by the ignition control signal S₁₅, generated at the time t₄, the output signal S₁₈ of the flip-flop circuit 16 is held at a high level, while the inverted output signal S₁₉ is held at the low level. The counter 7 counts the crank angle pulses S6 starting from the time t₄ but is not reset at the time t₅, so that the square wave signal S₁₀ is generated indicating a count greater than or equal to 90. Since the differential signal S₁₁ is produced from the rising edge of the signal S₁₀ by the differential circuit 9, and since both signal S₁₁ and S₁₈ are at the high level, the signal S₁₂ is output by the AND gate 10, so that the replacement ignition control signal S₁₄ is generated. Thus, the engine ignition system generates the ignition control signal without deficiency. As a result, in spite of the breakage of the coil of the magnetic sensor SN₁, the ignition plugs #1 and #4 are sparked. In a similar manner, even if the magnetic sensor SN₂ has a broken coil, the ignition plugs #2 and #3 will operate normally.

The crank steps of the engines are tabulated for reference in FIG. 4. FIG. 4(a) tabulates the crank steps of the series four-cylinder engine having a 360 degree crank and FIG. 4(b) tabulates the crank steps of the series two-cylinder engine having a crank of 180 degrees. In FIGS. 4(a) and 4(b), the circled letters EXP indicate the explosion stroke, the letters EXH indicate the exhaust stroke, the letters SUC indicate the suction storke, and the letters COMP indicate the compression stroke. The circles locted on the dividing lines between the different strokes indicate effective ignitions and the X's indicate ineffective ignitions.

FIG. 5 is a circuit diagram illustrating a second embodiment of the present invention. FIG. 5 illustrates an ignition pulse generating system which is applied to the V-type two-cylinder engine. For this configuration the magnetic sensors SN₁ and SN₂ which act as the reference position detecting sensors, are arranged about the circumference of magnetic disc P₁ and spaced 80 degrees apart. The circuit illustrated in FIG. 5 has substantially the same construction as that illustrated in FIG. 1, but is different in the portions corresponding to the decoder 8 and the leading edge differential circuit 9. As previously described, the counter 7 counts the crank angle pulses S₆ received at the clock pulse terminal CP and generates a counted value as the binary pulse signal. If the reset input signal S₉ arrives before the counted value reaches 40, the decoder 8-1 generates an output signal S₁₀₋₁ at a low level. If the reset input signal S₉ arrives after 40 pulses have been counted, square wave signal S₁₀₋₁ having a predetermined width and a high level is output by the decoder 8-1. A decoder 8-2 has its output signal S₁₀₋₂ held at the low level if the reset input signal S₉ arrives before the counter 7 counts 140 pulses S₆. The decoder 8-2 produces a square wave signal having a predetermined width and the high level if the reset input signal S₉ does not arrive. The decoders are well-known circuits which are comprised of a combination of AND gates.

The leading edge differential circuits 9-1 and 9-2 receive the square wave signals S₁₀₋₁, and S₁₀₋₂, respectively. The differential circuits differentiate the rising edge of the signals and generate differential outputs S₁₁₋₁ and S₁₁₋₂, respectively. The output signals S₁₁₋₁ and S₁₁₋₂ of the differential circuits are received by AND circuits 10 and 11, respectively. The primary and secondary wiring of ignition coils T₁ and T₂ each have one terminal which receives a +B voltage and each have another terminal connected to the ignition plugs #1 and #2, respectively.

The operation of the circuit illustrated in FIG. 5 will be described in its normal and abnormal states with reference to the time charts illustrated in FIGS. 6 and 7.

During normal operation the counter 7 is timely reset by the signal S₉. After the component of the signal S₈ has been received as the reset input signal S₉ the counter 7 is reset by the component of the signal S₇ when the count reaches 40, so that the output signals S₁₀₋₁ and S₁₀₋₂ produced by the decoders 8-1 and 8-2 are held at the low level. When the counter 7 counts 40 pulses S₆ after the arrival of the component of the signal S₇, the signal S₁₀₋₁ is produced which is a square wave having a predetermined width. The leading edge of this square wave is differentiated and passed as the signal S₁₁₋₁ to the AND circuit 10. However, AND circuit 10 has its output at the low level at this time, because the other input signal S₁₈ is at the low level. In other words, there is no change in the situation in which the signal S₁₀₋₁ is at the low level. When the counter 7 counts 140 pulses S₆, it is reset by the component of the subsequent signal S₈, so that the output S₁₀₋₂ of the decoder 8-2 is held at the low level. As a result, the output signals S₁₄ and S₁₅ produced by the OR circuits 12 and 13 are coincident with the position detection pulses S₇ and S₈, so that the ignition plugs #1 and #2 are alternately sparked due to the switching operations of the transistors TR₁ and TR₂.

When the coil of one of the magnetic sensors SN₁ or SN₂ is broken, the operation of the circuit illustrated in FIG. 6 is illustrated in FIG. 7, and will hereinafter be described. For this example it is assumed that the magnetic sensor SN₂ has its coil broken during the period between time t₄ and time t₅.

Because a reset input signal S₉ is not present at the time t₅ when 40 pulses S₆ are counted, the output signal S₁₀₋₁ of the decoder 8-1 becomes a square wave having a predetermined width. The differential pulses S₁₁₋₁ which indicate the rising edge of the square wave are produced by the leading edge differential circuit 9-1. At this time, since the output S₁₈ of the flip-flop 16 is at the high level, the output signal S₁₂ produced by the AND circuit 10 is a pulse at the high level, so that the ignition control signal S₁₄ is produced by the OR circuit 12. As a result, even in the absence of the position detection pulses S₇ or S₈, the replacement ignition signal S₁₄ is generated so that the sparking operations of the ignition plug #1 continue. Alternatively, if the coil of the magnetic sensor SN₁ is broken, the replacement pulses for ignition control are similarly obtained as the signal S₁₅ produced by the output signal S₁₀₋₂ of the decoder 8-2, so that the normal running of the engine is maintained.

As has been hereinbefore described, according to the present invention, the ignition control signals can be generated at the normal operation timing even when the circuit for generating reference position detection pulses is malfunctioning in both the series four-cylinder engine having a 360 degree crank, or the series or V-type two-cylinder engine having a 180 degree crank. As a result, it is possible to prevent the engine from stopping.

The many features and advantages of the invention are apparent from the detailed specification and thus it is intended by the appended claims to cover all such features and advantages of the system which fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 

What is claimed is:
 1. An engine ignition system, operatively connected between an engine crank and sparkplug ignition coils, comprising:crank angle sensing means, secured to the engine crank, for sensing the angle of the engine crank and for generating crank angle signals therefrom; reference position signal generating means, secured to the engine crank, for sensing a reference position of the engine crank and for generating first and second reference position signals therefrom; signal processing means, operatively connected to said crank angle sensing means and said reference position signal generating means, for generating primary ignition signals, said signal processing means including means for detecting the absence of the first or second reference position signals and for generating replacement ignition signals when either the first or second reference position signals are absent; and switch means, operatively connected between the sparkplug ignition coils and said signal processing means, for turning the ignition coils on in dependence upon the primary ignition signals or the replacement ignition signals.
 2. An engine ignition system as recited in claim 1, wherein said means for detecting and generating comprises:a counter, operatively connected to said crank angle sensing means and said reference position signal generating means, for counting the crank angle signals and being reset by the first and second reference position signals; a decoder, operatively connected to said counter, for generating a decoder signal in dependence upon a predetermined count value counted by said counter; a flip-flop for generating flip-flop signals; a first logical circuit, operatively connected to said decoder and said flip-flop, for generating a logic signal in dependence upon the decoder signal and the flip-flop signals; and a second logic circuit, operatively connected to said reference position signal generating means, said first logic circuit, said flip-flop and said switch means, for generating the primary ignition signals or the replacement ignition signals in dependence upon the first reference pulse, the second reference pulse and the logic signal, the primary or replacement ignition signals setting and resetting said flip-flop.
 3. An engine ignition system as recited in claim 2, wherein said means for detecting and generating further comprises:a leading edge differential circuit operatively connected between said decoder and said first logic circuit; a trailing edge differential circuit operatively connected between said second logic circuit and said flip-flop;and an OR circuit operatively connected between said reference position signal generating means and said counter.
 4. An engine ignition system as recited in claim 2, wherein said first logic circuit comprises first and second AND circuits operatively connected to said decoder, said flip-flop and said second logic circuit.
 5. An engine ignition system as recited in claim 2, wherein said second logic circuit comprises first and second OR circuits operatively connected to said reference position signal generating means, said first logic circuit, said flip-flop and said switch means.
 6. An engine ignition system as recited in claim 1, wherein said switch means comprises first and second transistors operatively connected between said means for detecting and generating and the ignition coils.
 7. An engine ignition system as recited in claim 1, wherein said crank angle sensing means comprises:a crank angle sensor means, secured to the engine crank, for sensing the angle of the engine crank and for generating the crank angle pulses therefrom; and a crank angle wave shaping circuit operatively connected to said crank angle sensor means and said signal processing means.
 8. An engine ignition system as recited in claim 7, wherein said crank angle sensor means comprises:rotating means, secured to the engine crank, for rotating at the same rate as the engine crank; a crank angle magnetic disc secured to said rotating means and having teeth formed on the periphery of said crank angle magnetic disc;and a crank angle magnetic sensor, positioned across from the periphery of said crank angle magnetic disc in the magnetic field of said crank angle magnetic disc, for generating the crank angle pulses each time one of the teeth passes said crank angle magnetic sensor.
 9. An engine ignition system as recited in claim 1, wherein said reference position signal generating means comprises:reference sensor means, secured to the engine crank, for sensing the reference position of the engine crank and for generating the first and second reference pulses therefrom; first and second reference wave shaping circuits operatively connected to said reference sensor means; and first and second trailing edge differential circuits operatively connected between said signal processing means and said first and second reference wave shaping circuits, respectively.
 10. An engine ignition system as recited in claim 9, wherein said reference sensor means comprises:rotating means, secured to the engine crank, for rotating at the same rate as the engine crank; a reference magnetic disc secured to said rotating means and having a tooth formed on the periphery of said reference magnetic disc; a first reference magnetic sensor, positioned at a first position across from the periphery of said reference magnetic disc and in the magnetic field of said reference magnetic disc, for generating the first reference position pulse each time the tooth passes said first reference magnetic sensor; and a second reference magnetic sensor, positioned at a second position across from the periphery of said reference magnetic disc and in the magnetic field of said reference magnetic disc, for generating the second reference position pulse each time the tooth passes said second reference magnetic sensor. 